David Cunliffe has been forced to defend Labour's baby bonus policy, after his announcement failed to say some parents wouldn't get the $60 per week payment.

In his state of the nation speech on Monday, the Labour leader promised that "for 59,000 families with newborn babies, they will all receive a Best Start investment of $60 per week, for the first year of their child's life".

However, those who are on paid parental leave, worth up to $488 a week - about 25,000 people a year - will not receive the payment at the same time.

The exclusion was included in Labour's background material but not in Cunliffe's speech.

This morning, Cunliffe told Firstline he could have swapped the word "will" for "can".

"Our materials which we published at the time of the speech made it clear right from the get-go, that people have a choice," he said.

"They can either take the bonus, so called, for the whole year, which they are entitled to do, or if they are also eligible they can choose to be on paid parental leave which is a greater amount – so they're never going to be worse off than the $60 a week.

"One word in the speech could have been different - 'will' or 'can' - not a big drama."

Labour's welfare spokeswoman Jacinda Ardern said it might have been more accurate if the speech had said "in the first year of the child's life" but there was no intention to deceive.

"It makes no sense to have a duplicate payment."

But Prime Minister John Key said Cunliffe's claim was not true.

"Firstly 25,000 of them get paid parental leave and they certainly will not get that for 52 weeks," Key said.

"Also, those receiving a parental tax credit, which is 15,000, in the fine print we now find out they also won't get that payment."

That meant only one in three of the 59,000 would get a full year payment.

"What that means actually is the only people who get 52 weeks at $60 per week are fundamentally beneficiaries and those earning $150,000 a year."

However, Labour made it clear on the day of Cunliffe's speech that the eight-week long parental tax credit, a maximum of $1200 paid to those who did not qualify for paid parental leave, would be dumped.

Ardern said those people would instead qualify for the baby bonus and get more cash from that - $3120 over a full year.

She said Key was "entirely wrong" to say only beneficiaries and those earning $150,000 a year would get the full 52 weeks.

Beneficiaries and low income families would also continue to receive the $60 a week payment for the second and third year of their child's life if their income was under $50,000 a year, and lesser amounts up to an income of $77,000.